+47.64754, -122.34736
47°38'51" N, 122°20'50" W
Source: National Bridge Inventory
Information not verified. Use at your own risk.


Name:SR 99 over LAKE UNION
Structure number:0001447A0000000
Location:7.7 N JCT SR 509
Purpose:Carries highway and pedestrian walkway over highway, waterway, and railroad
Route classification:Principal Arterial - Other Freeways or Expressways (Urban) [12]
Length of largest span:799.9 ft. [243.8 m]
Total length:2955.2 ft. [900.7 m]
Roadway width between curbs:56.4 ft. [17.2 m]
Deck width edge-to-edge:69.6 ft. [21.2 m]
Vertical clearance below bridge:134.8 ft. [41.1 m]
Owner:State Highway Agency [01]
Year built:1931
Historic significance:Bridge is on the National Register of Historic Places [1]
Design load:M 18 / H 20 [4]
Number of main spans:8
Main spans material:Steel [3]
Main spans design:Truss - Deck [09]
Deck type:Concrete Cast-in-Place [1]
Wearing surface:Bituminous [6]

Latest Available Inspection: August 2017

Good/Fair/Poor Condition:Fair
Status:Open, no restriction [A]
Average daily traffic:58,319 [as of 2012]
Truck traffic:3% of total traffic
Deck condition:Satisfactory [6 out of 9]
Superstructure condition:Fair [5 out of 9]
Substructure condition:Satisfactory [6 out of 9]
Structural appraisal:Somewhat better than minimum adequacy to tolerate being left in place as is [5]
Deck geometry appraisal:Basically intolerable requiring high priority of replacement [2]
Underclearances appraisal:Somewhat better than minimum adequacy to tolerate being left in place as is [5]
Water adequacy appraisal:Equal to present desirable criteria [8]
Roadway alignment appraisal:Equal to present desirable criteria [8]
Channel protection:Banks are protected or well vegetated. River control devices such as spur dikes and embankment protection are not required or are in a stable condition. [8]
Pier/abutment protection:Navigation protection not required [1]
Scour condition:Bridge foundations determined to be stable for the assessed or calculated scour condition. [8]
Operating rating:40.9 tons [37.2 metric tons]
Inventory rating:24.0 tons [21.8 metric tons]
Sufficiency rating:46.9
Recommended work:Bridge rehabilitation because of general structure deterioration or inadequate strength. [35]
Estimated cost of work:$69,738,000

Previous Inspections

DateSuff. RatingConditionDeckSuperstructureSubstructureSD/FOADT
August 201746.9FairSatisfactoryFairSatisfactoryFO58319
August 201546.5FairSatisfactoryFairSatisfactoryFO58319
August 201346.5FairSatisfactoryFairSatisfactoryFO58319
August 201144.4FairSatisfactoryFairSatisfactoryFO69463
December 200944.1FairSatisfactorySatisfactoryFairFO71085
June 200755.2FairSatisfactorySatisfactorySatisfactoryFO73836
May 200553.2FairSatisfactorySatisfactorySatisfactoryFO73836
July 200353.2FairSatisfactorySatisfactorySatisfactoryFO73836
March 200153.2FairSatisfactorySatisfactorySatisfactoryFO73836
June 199953.2FairSatisfactorySatisfactorySatisfactoryFO73836
May 199759.3FairSatisfactorySatisfactorySatisfactoryFO73836
May 199527.9PoorSatisfactoryPoorSatisfactorySD73836
June 199329.3PoorSatisfactoryPoorSatisfactorySD59363
January 199227.8PoorFairPoorSatisfactorySD59363